Abstract

The "completion of calls" feature defined in this specification
allows the caller of a failed call to be notified when the callee
becomes available to receive a call.
For the realization of a basic solution without queuing, this
document references the usage of the dialog event package (RFC 4235)
that is described as 'Automatic Redial' in "Session Initiation
Protocol Service Examples" (RFC 5359).
For the realization of a more comprehensive solution with queuing,
this document introduces an architecture for implementing these
features in the Session Initiation Protocol where "completion of
calls" implementations associated with the caller's and callee's
endpoints cooperate to place the caller's request for completion of
calls into a queue at the callee's endpoint; when a caller's request
is ready to be serviced, re-attempt of the original, failed call is
then made.
The architecture is designed to interoperate well with existing
completion of calls solutions in other networks.